This receipe I got off Alex Anderson quilt site, 1 gal of wm water, 1 qt of buttermilk, 2 tbl of lemon juice, it will not hurt the fabric at all so you can soak it for hours until the rust spots are gone, you can double or trible or everhow many times need to soak the quilt, rinse well in mild soap and line dry. It will also brighten dull fabric.